1. Field of the Invention
The present invention relates to a device for treating liquids with UV-radiation.
2. The Prior Art
These devices are preferably used in sewage purification (or treatment) plants. Before the purified (or prepurified) waste water effluent from the sewage treatment plant is discharged into natural waters, it always has to be disinfected a number of times. The waste water purified in the treatment plant is for this purpose subjected to a treatment with ultraviolet radiation (UV-radiation).
The devices provided for such treatment have an irradiation chamber through which the waste water flows. The irradiation chamber is equipped with UV radiation sources. These sources are formed by UV radiation lamps, which are enclosed in protective tubes made from quartz for protecting the lamps against the waste water. These protective tubes are permeable to the UV-rays which, therefore, can penetrate the waste water.
In addition to the irradiation chamber, the known devices comprise an outlet chamber arranged downstream of the irradiation chamber. The waste water exposed to the UV-radiation is received in the outlet chamber; and the now-purified, disinfected waste water can be discharged from there into the discharge system.
EP 0 687 201 B1 discloses a purification device with an irradiation chamber designed in the form of a completely closed chamber shaped like a tube. The waste water is forced through the irradiation chamber under pressure, which leads to an increased flow rate of the waste water in the irradiation chamber.
In such devices, the outlet chamber adjoining the irradiation chamber in the downstream direction has installed elements in the form of terminating walls serving as weir elements. The terminating walls are designed, for example, in the form of shutoff flaps (or shutters), overflow weirs or motor weirs extending vertically relative to the direction of flow of the flowing waste water. The water dams up in front of the installed elements. The water then flows off over the so-called overflow edges into the discharge system. Thus the water flows over the upper edges or below the shutoff flaps or shutters, and is then admitted into the natural waters.
In the known devices, the installed elements of the outlet chamber serving as weir elements comprise a plurality of rectangular or also triangular individual chambers with vertical termination walls serving as damming walls. These elements are installed next to each other. This increases the overall length of the overflow edge for the waste water. Therefore, even relatively large quantities of waste water can flow off over the overflow edge and then be discharged into the drain system without substantially raising the water level.
Since the known devices require a great overall length for the available overflow edge in order to avoid high variations in the water level, the dimensions of the chambers are very large when viewed in the direction of flow of the waste water. Thus the complete device requires a great deal of overall space. This, furthermore, leads to increased expenditures with respect to manufacturing and operating costs.
Another drawback is that the waste water received in the outlet chamber from the irradiation chamber impacts quasi-vertical termination walls of the elements installed in the outlet chamber. This impact will slow down the water contacting these walls. This causes the water to back up, and such backwater may extend back into the irradiation chamber upstream. This will lead to uneven flow of the waste water. Such nonuniform flow, however, is disadvantageous for treating waste water with UV-radiation. It is possible to provide a free space between the irradiation chamber and the outlet chamber. This free space is in the form of a calming zone for the flowing waste water in order to prevent the back-up of water from extending back into the irradiation chamber. However, such a calming zone increases the overall dimensions of the device even more, so that the costs of such a device are further increased again.